can’t pass queryselector values to an object JavaScript [duplicate]

I’ve been creating a booklist app by a tutorial, which is OOP JavaScript, but I’m having troubles assigning values to an object. User writes title, author and isbn of the book and then adds it to the booklist. The problem is that all of the three values (title, author, isbn) display as undefined once added to the booklist. My code is exact same as one in video tutorial and I dont know what is the problem.

class Book {
    constructor(title, author, isbn){
        this.title;
        this.author;
        this.isbn;
    }
}

document.addEventListener('DOMContentLoaded', UI.displayBooks);
document.querySelector('#book-form').addEventListener('submit', (e) => {
    e.preventDefault();

    const title = document.querySelector('#title').value;
    const author = document.querySelector('#author').value;
    const isbn = document.querySelector('#isbn').value;
    console.log(title);
    console.log(author);
    console.log(isbn);
    const book = new Book (title, author, isbn);
    console.log(book);
    UI.addBookToList(book);
});

As you see, I console.logged all variables to make sure that their values are okay. However, when I console.log(book) it doesn’t show it in the console correctly, just it’s name and type. So I think the problem here is that the program fails to pass values to the object.

I feel kinda stupid, because I’ve checked the comments under the video tutorial and nobody was having any problems. It’s my first JS project and I’m really confused.